Propeller



Feb. 28, 1933. w STELZER 1,899,650

PROPELLER Filed April 21,.v 1928 Patentecl Feb. 28, 1933 UNITED STATES PATENT OFFICE WILLIAM STELZER, DIE CHICAGO, ILLINOIS, ASSIGNOB T0 AMERICAN PROPELLIER COM- IANY, OIE BAL'IIMORE, MARYLAND, A CORIORATION OF MARY LAND IPBOIPELL'ER Application filed April 21,

T he invention relates 130 improvements of propellers operating yaw, i. e. in movement relative to the air in a line oblique to the line of the shaft, specifically when such angle of obliquity is large, as in case of helicopt-er flight with the propeller serving for both sustentation and traction, and also in flight of other types 0f aircraft subjected to yaw, as airplanes and aerostats.

The objects of the improvernents are, first, to support the propeller rotatably in a bearing whose centroiglal axis is parallel to the centroids of the propeller blades and perpendicular 130 the propeller axis; second to give the blades such a form, that the line 0f action upon which the airforce aets, i. e. the center of pressure of the propeller section is between the centroidal axis of the above mentionecl bearing and the trailing edge of the blades, to efl'ect continuous mutual balancement of the blades.

It is well known that present day propellers designed for normal strain, besides exerting a lateral er sicl'e thrusl: acting from theshaftt0 its bearings, flutter when operating uncler conditions 0f niovement oblique to the propeller axis due to the lack of symmetry 0f the air stream relative t0 the propeller shaft and the resulting lack 0f symmetry between the two opposite blades of the ropeller in their relation to the air stream.

The aim of my present invention is to 0btain an equal force in each blade and to eliminace fiuttering. I attain this by the simple arrangement of parts described in particular hereinafter; whereas the forwardly moving blade, which produees a gr eater force reac tion than the other, will incrase the angle of attaek of the latter and decrease its 0wn until the reaction is equal on b dth blades.

Another object is to make the ropeller reversible in its position in order that it may serve as a brake after lancling 0n the? ground; so that when the rotation of the drive-shaft is reversed by means of reversing gear, the propeller Will turn automatically 180 and face backward, whereby the full efficiency is used to bring the aircraft to a halt.

Further objects of the invention Will ap- 192 8. Seria'l N0. 271,820.

pear in the following detailed description and the accompanying drawing wherein:

F ig. 1 shows a front view of the improved are n'ot intended primarily es terms of limi-' tatiom The roots 1 of the blades 2 are rigidly secured to the metal sleeve 3 turning freely in a divided bearing consisting of the bearing cap 4 and the casing 5 formed on to the driveshaft 6 supported by a framell, which may be part 0f the power plant or aircraft. From the bearing cap 4 and the casing 5 projecfi the lugs 7 provided t0 receive screws or any other appropriate means to secure the parts 4 and 5 together, which, with the balls 8, form an antifriction b earing for the ropeller, so that it may turn freely and react instantly -upon the fluctuations of the relative Wind velocities. The flanges 9at the terminations Cf the sleeve 3 and the flanges 10 projecting from the casing 5 and theadjacent bearing cap 4, besides serving as a reinforcement, keep the balls 8 in the proper. place and also prevent motion endwise of the sleeve 3.

It is evident that a propeller equipped with the described improvement, but with a present day arrangement elf-the blades, would produce no beilancing efi'ect, but would even turn into any osition. T0 attain the desired object, the largest part of the blade surface is located rearward of the bearing axis YY, whereby the line of action upon which the airforce acts,- is between the bearing axis YY and the trailing edges of the blades. In this arrangement the airforce acting on one blade t ends to decrease the angle of attack, but is -counterbalanced by the airforce acting 011 the opposite blade. N ow as the airforce 011 one blade increases,due, for in- 100 stance, to lack of symmetry of tl1e air stream relative to the propeller axis-the angle of attack decreases in this blade and'consequent- 1y inereases in the other. As it is known that the angle of attack is a faclzor cf the resultant foree, it may be readily understood that the decrease of the angle of attack of the blade with greater reaction and the increase of the angle of attack of the other brings about an approximation of the reactions acting on the two blades.

In Fig. 4 a modification of the invention is illustrated showing the leading edge 0f the blades 2 at an acute angle with the axis Y'-Y .of the bearing. The object of tl1e arrangement may be seen readily as the beating m0- tions of the blades, due to the lack of symmetry of the air stream relative 130 the pro-.

peller shaft and the resulting lach 0f symmetry between the two opposite blades of the -ropeller in their relation to the air stream, will add to the balancing eifect caused by the automatic adjustment 0 the angle of attack. Another feature is due to the resulting gymstatic action upon the blades, by preventing any possible oscillation of the propkaller.

While there are herein shown and' described the preferred embodiments 0f my invention, it shall nevertheless beunderstood tl1at changes may be made without departing from the scope of the invention; some of the most obvious modifications will be briefly stated:

In this preferred embodiment described hereinbefore a. bearing embracing the propeller-blade roots has been employed in order to permit th e ropeller to face backward when the rotation 0f the drive-shaft has reversed, to stop the aircraft after alighting;

nevertheless, other suitable means for counecting the Propeller rotatably to the driveshaft may be employed, such as hinges, er joints connected by pins.

While by constructing a wooclen propeller it will be desirable to carve' it from one piece of laminated wood and thus make the sleeve 3 of two portions, by making the blades of metal, the said sleeve diagrammatically in the drawi ng andserve as a. medium fo r rigid connection of the two blades.

- T0 conform eraft, the propeller rake may suitably be varied, as it has no eflect upon the dominant features 0f the invention.

Itshall be w'ell may .be made for plications, such as for helieop ters, aerostats, 01 marine vessels. There'fore I do n0t desire t0 be limited in the applicat ion 015 rny invention,

- the aflixed drawing.

modifications and variations may 'be resorted 3 may be used as shown With tlie difierent types of airunderstood that changes the diiferent kinds of apangularly disposed with respect to the rofiational axis of said blades.

2. An air craft propeller comprising a plurality of blades, means for rigidly securing the inner ends f said blades said blades lying substantially in the same plane, a hub, means the first-named means in said hub said supporting means maintaining the blades at acute angles with respeet to the axis abt which the said blades are rotatable, th e leading edges 0f the blades being more closely together the for rotatably supportirig adjacent-the said axis than the trailing edges.

3. An air craft propeller comprising a plurality of rigidly interconnected blades the said blades lying st1bstantially in the sameplane, and means for rotatably mounting said interconnected blades, each' of said blades being angularlydisposed. With respect to the axis about which the blades are. rotatable.

4-. A propeller for aircraft borhprishg a pair of blades having tapered tip p0rtions, means for rigidly in'terconnecting the blades in such a manner that the blades will lie in substantially the same plane'means for rotatably' mounting the intercomiected blades, each of the blades being angularly disposed with respect to the axis about which the blades are rotatable and -having the leading edges thereeof more, closely adjacent the sa1d axis than the trailing edge's.

' WILLIAM STELZER.

1101 in tl1e appencle claims, to the particular embodiment pointed out in 

